In recent years, a digital camera has been reduced in size, and a mobile phone having a function of the digital camera has been widely used. Accordingly, an imaging device is also required to be reduced in size, and a further improvement in quality is also required. Patent Document 1 discloses that when an imaging device is manufactured, a vent for releasing thermally expanded air is provided, and the vent is blocked after the thermally expanded air is released in order to prevent dust or the like from entering through the vent.